Little is known about the vault except that it has been mentioned several times in several places. One certain truth is that it will require at least 12 codes to open it.
We know that, among other things, the Volume 1 vault required:
- The first digits are on a brass tag
- The second digits are on a brass tag
- The third digits are what the pictures have in common
With the prologue issue, several members did in fact receive brass tags. One was stamped with "A 0571", and another with "Q 8296", with "MPC" stamped on the reverse.
From the Issue 2, Knick Knack Metropolis, crossword, we learn that the vault will require 12 codes, including words and numbers. It also indicates that more clues can be found "in all sorts of strange places".